Carrier-telegraph repeater circuits



July 19, 1927.

B. P. HAMILTON CARRIER TELEGRAPH REPEATER CIRCUITS Filed oct. 24. 1925 2Sheets-Sheet` 1 IN VEN TOR A TTORNEY Jul 19 1927.

y v B. P. HAMILTON CARRIER TELEGRAPH REPEATER CIRCUITS 2 sheets-snee'. 2

Filed 00t- 24. 1925 s mhh,

ABY

ATTORNEY Patented July 19, 1921.

BAXTER P. HAMILTON, OF RIVER EDGE, N

EW JERSEY, ASSIGNOR T0 AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, ACORPORATION OF NEW YORK.

CARRIER-TELEGRAPH REPEATER CIRCUITS.

Application led October This invention relates to repeater statien's formultiplex signaling systems employing carrier currents, and moreparticularly to arrangements whereby intermediate subscribers drops maybe obtained at such repeater stations.

Two types of repeater equipment have heretofore been used for carriertelegraph systems. In the one type, individual repeating devices areprovided for each channel of the system. In the other type, a. s inglerepeater circuit is used for an'iplifying all of the channelstransniitting in ar given direction. In a repeat-er arrangement of thefirst type, intermediate tubscribers drops may be readily provided forin connection wit-li the repeater equipment, since each channel has itsown individual repeater equipment. Amplifying equipment cemm-on to aplurality of channels would involve certain economies and wouldordinarily be used where there is no necessity for separating thecarrier channels one from the other. There are occasions. however, whereit is desirable to provide local subscribers drops at the repeaterstation for one or more o-f the channels wit-hout disturbing theeffectiveness of the common repeater for amplifying all of the channels.

One of the objects of the present invention is to provide an arrangementwhereby intermediate subscribers` drops may be obtained for one or moreof the channels of a multiplex carrier system at a repeater sta tion ofthe type in which the amplifying equipment is common to all of thechannels transmitting in a` given direction. Other and further objectsof the invention, will be clear from the following description when readin connection with the. accompanying drawing, the figures of' whichillustrate certain diagrams embodying two modifications of' theinvention.

Referring to Figure l, L and L represent carrier transmission linesections over which a plurality of carrier currents of a multiplextelegraph system may be transmitted. The lines are shown interconnectecthrough a carrier repeater involving an ainplier unit AE for amplifyingthe carrier currents of all of the channels transmitting from west toeast, ay similar amplifier AW being provided for amplifying the carriercurrents of all of the channels transmitting from east to west. Eachamplifier is in- 24, 1925. Serial No. 64,685.

eluded in a separate transmission path at the repeater station, eachpath being used for transmission in one direction only. In systems ofthis type, the carrier frequencies used for transmitting` in onedirection are all included within one range of frequencies, and all ofthe carrier frequencies used for transmitting in the opposite directionare included Within another range of frequencies. For example, thesystem may involve ten channels transmitting from west to east oncarrier frequencies ranging from 3330 cycles per second to 550() cyclesper second, and ten similar channels transmitting from ,east t-o west oncarrier frequencies ranging from 6500 cycles to 10,000 cycles. Low passfilters EF and EF inserted on either side of the amplifier AE willenable the first group of' carrier frequencies above mentioned to betransmitted through the amplifierAE While preventing the second groupfrom being transmitted by said amplifier'. Similarly, high pass filtersWF andv WF included on either side of the amplifier AW will 4insure thatonly the carrier frequencies of the second group will be transmittedthrough said amplifier AW.

The filters above referred to are known as directional filters by reasonof the fact lthat they separate the carrier frequencies of the channelsat the repeater station ac cording to the direction of transmission. Itwill be noted, however, that no provision is made for separating thecarrier frequencies as between individual channels. In ordei thatintermediate subscribers drops may be` provided in connection witlianygiven ti'ansmission channelg some arrangement must be provided forsegregating the particular frequency corresponding to that channel fromall other frequencies at the subscribers station. The apparatus shown inFig. l is arranged to segregate two or moi'e carrie-r frequencies fromeach directional band for the purpose of obtaining intermediatesubscribers drops for those channels. For this purpose a bandsuppression filter SFE of a vwell-known type is inserted on the outputside of the amplifier AE. to prevent the direct transmission of thecarrier frequencies and side band frequencies corresponding to 3330 and3570 cycles, for example, from the amplifier to the transmission linesection L. A resistance bridge 21 is connect-ed across the output` ofthe amplifier, and the two carrier frequencies just referred ,to aretransmitted through the bridge to lsuitable selective circuits EIN, andEF9. 'fhese frequencies are thus selected and impressed upon terminalreceiving equipment of the ordinary type involving in the case of thefrequency of 3330 cycles an amplifier A and a detector D, and areceiving relay RR Vconventionally indicated in the drawing.

Similar receiving equipment is provided in connection with the selectivecircuit EB", This receiving equipment will enable the local operator toreceive signals on the channels corresponding to the vtwo frequenciesjust referred to. Y Y

In order to enable the local operator to transmit at frequenciescorresponding to the suppressed channels, a similar resistance bridge 22is connected across the opposite side of the suppression filter SFE, andconductors from said bridge lead to similar selective circuits such, forexample, as tuned circuits EF, and EFW Carrier ti" iismitting equipmentof the usual terminal type is associated With each of these selectingdevices.y for example, the transmitting equipment associated With theselectivev device EFM comprises a Vsending relay SR arranged toshort-circuit the input of the modulator M in accordance With the dotsand dashes of the code, the modulator M being supplied with a carrierfrequency of 3330 cycles from a suitable local oscillator.

Arrangements are also provided whereby the signals corresponding to eachof the'suppressed channels may be transmitted through the localsubscribers drops from the vline L to the line L. For this purpose, thereceiving relay RR controls, by its armature, not only the usual polarsounder, but the polarity ot current applied to a local subscribers loop31 which is connected through a keyl l to the second relay SR". rIhus,in the normal operation of the circuit, the carrier frequency of 3330cycles, which is suppressed by the filter SFE, is selected by the filterEFU, so that the signals superposed thereon may be detected by thedetector D, to operate the receiving relay RR. The latter relay thentransmits the signals through the local relay 81 in a Well-known mannerto operate the sending` relay SR which in turn causes an interruption ofthe carrier frequencies of 3330 cycles from the local oscillator O, sothat the carrier signals are then transmitted through the selectivecircuit EFM, and filter EF tothe line L. The local operator may receivethe signals by means of the polar sounder associated ivith the relay RR,and when signals are not being` received from the line L, may operatethe Key K to transmit signals over the line L. In a like manner, thereceiving equipment corresponding to the channel requiring a carrierfrequency of 3570 cycles and conventionally indicated in the drawing,may be connected by another subscribers loop 82 to permit a. similaroperation at the local repeater station.

In order to provide intermediate subscribers drops in connection withthe corresponding channels transmitting from east lo West, a suppressionlter SFV of a Welllmovvn type is included in the output circuit of thean'iplifier AV to suppress the carrier frequencies and side bandfrequencies of say 9500 cycles and 10,000 cycles. These particularfrequencies are led through a resistance bridge 23 to receivingequipment similar to that already described, except that selectivedevices IVFQ, and VVFm are arranged to select respectively thefrequencies of 9500 cycles and 10,000 cycles. Likewise, on the oppositeside of the suppression filter SFlV, another resistance bridge 24 isprovided, and this bridge is connected to transmitting equipment similarto that already described, except that the selective devices in thiscase will be selective of 9500 cycles and 10,000 cycles, respectively,and the local oscillators will be arranged to generate these tivofrequencies. Local subscribers loops 33 and 34 connect the tivo groupsof sending and receiving equipment so that by means of the ley K, forexample, the operator may signal at the frequency of 10,000 cycles tothe line L when no signals are being received at that frequency from theline L. If signals are being transmitted at the carrier frequency of10,000 cycles over the line L', such .signals may be received by thelocal operator through the control exercised by the receiving relay RRover the usual polar sounder. The relay RR at the same time transmitsthe detected signals over the loop 3? so that the sending relay SR isactuated to relay the signals through the modulator M, filter TF-,0 andfilter IVF to the line L.

Fig. 2 shows a modified arrangement which is particularly adapted foruse where only one carrier channel in each direction is to be used foroperating an intern'iediate subscribers drop. In this case, thearrangement of the repeater apparatus is identical With that describedin connection with Fig. 1, except that the suppression filters SITE andSFW are omitted. A resistance bridge 21 is connected across the inputside of the amplifier AE and leads to a selective circuit EFM, forselecting the carrier frequency ot 3330 cycles used for transmittingfrom n'est to east. The usual receiving equipment comprising amplifierand detector D, and a receiving relay RR is associated with the tunedcircuit. In this instance, the carrier frequency just referred to is notsuppresrzed from the repeater path, but is transmitted through theamplifier, and a circuit EF1, tuned to the frequency of 3330 cycles isarranged to be bridged across the output side i' lilo of the repeaterunder the control of the sending relay SR. Vhen no signals are beingti'ansinitted through the repeater at this frequency, the carrierfrequency is steadily maintained upon the circuit, and when the tunedcircuit EFU, is closed, the carrier frequency will be suppressed andprevented from being trai'isp'iitted to the line section L. Accordingly,this carrier frequency may be suppressed in accordance with the code byoperating the sending ielay SR by means of a key K or a key K1 includedin a local subscribers loop. rlhe receiving relay RR controls, inaddition to the usual polar sounder, another loop leading to a localsounder 4,1. By means of said sounder, the local operator may receivesignals transn'iitted from the line L at the carrier frequency of 3330cycles. As already stated, signals may be transmitted to the linesection L at this frequency by operating the key K or K1 to open andclose the tuned circuit EF 10. This, ofcourse, would only be done whenno signals are being transmitted at this frequency over the line L.lVhen signals are transmitted over the line L at this frequency, theywill pass through and be amplified by the amplifier AE and thustransmitted directly to the line L in the usual manner.

\ For the corresponding channel transmitting from east to west, forexample, the channel employing the carrier frequency of 10,000 cycles, asimilar receiving equipment is connected with the bridge 23 associatedwith the input side of the amplifier AWV. Likewise, similar transmittingequipment is connected to and controls the tuned circuit 7F10 so thatsaid tuned circuit may be bridged across the output side of theamplifier AW then no signals at the carrier frequency of 10,000 cyclesarev being transmitted over the line L, the operator may employ eitherkey K or K,L to transmit signals at the carrier frequency of 10,000cycles to the line L. Vhen signals ai'e being transmitted at thiscarrier frequency over the line L, they will bereceived `by 'means ofthe receiving apparatus associated with the bridge 23, thereby causingthereceiving relay RR to operate the sounder 43 .as well as the usualpolar sounder. At the same time, the carrier frequency upon which thesignals are superposed will be transmitted through the amplifier AWV inthe usual manner for transmission over the line L to a distant station.

Should the operator desire to sinniltane- 'ously transmit to both theline L and the line L, switches 51 and 53 will be thrown to theiralternative positions, thereby connect- Aing the loops associated withthe sending relays SR and SR together in series. Wlhen so connected, theoperation of anyofwthe Akeys K, K1, K.1 and K will result in operatingboth relays;1 SR `and SR thereby transmitting signals at the carrierfrequency 3330 cycles to the line L and at the carrier frequency 10,000cycles to the line L.

It will be obvious that the general principles herein disclosed may beemployed in many other organizations widely different from thoseillustrated without departing from the spirit of the invention asdefined `in the following claims.

What is claimed is:

1. In a signaling system, a pair of transmission lines interconnectedthrougha common amplifier, so that a plurality of carrier frequenciestransmitted from one line to the other in the same direction areamplified by said common amplilier, means for obtaining an intermediatesubscribers drop at the repeater station comprising a bridged circuitassociated with the amplifierl path, a selective device connected withsaid circuit for selecting from said amplifier path a carrier frequencyincoming from one of said lines without interfering with thetransmission of other carrier frequencies over the ampli- .tier path tothe other line, and carrier receiving equipment associated with saidselective device, said carrier receiving equip-` ment including areceiving relay for operating local. Morse receiving equipment.

ln a signaling system, a pair of transmission lines interconnectedthrough a common amplifier, so that a plurality of carrier frequenciestransmitted from one line to the other in the saine direction areamplified bysaid common amplilier, means for obtaining an intermediatesubscribers drop at the repeater station comprising a bridged circuitassociated with the amplifier path, a selective device connected withsaid circuit for selecting from said amplifier path a carrier frequencyincoming from one of said lines without interfering with thetransmission of other carrier frequencies over the amplifier path to theother line, carrier receiving equipment associated with said select-ivedevice, said carrier receiving equipment including a receiving relay foroperating local 'Morse receivingl equipment, and means-controlled bylocal Morse sending apparatus for transmitting signals to said lastmentioned line upon a carrier frequency corresponding to the frequencyselected into said receiving equipmen y 3. ln a signaling system inwhich a common ,amplifier is employed for amplifying all ofthe carrierfrequencies` transmitting in one direction, and another'commonaniplilier is employed for amplifying all of the carrier frequenciestransmitting in the opposite direction, means for obtaining intermediatesubscribers drops comprising a bridged circuit asociated with eachamplilier, a selective device connected to each bridged circuit, one ofsaid selective devices subscribers drops comprising beingselective of afrequency used for transmitting in one direction, and the other selec--ti-ve `device bei-iig selective of one of tlie frequencies `used fortransmitting in tlie opposite-direction, and carrier receiving.equipiment ,associated vvitli eacli selective circuit,

said carrier receiviiig equipment including selective of one of tbcfrequencies used for transmitting in tlie voppositi-i direction, carrieryreceiving equipment associated 'With eacli selective circuit, saidAcarrier receiving equipment incliuling means for operating local Morsereceiving apparatus, andineans comprising` local Morse sendinglequipment for controlling the transmission of signals at carrierfrequencies corresponding to eacli of tlie carrier frequencies selected.

5, In a signaling Tstein in ivliicli tlie carrier frequenciescorresponding to a plurality .of Ichannels ti,:-.nsmitting in the samedirection are amplified by a common aniplilier, means for obtaining`intermediate subscribers loops comprising av bridged circuit associatedivitli tlie patli of said amplifier, -a selective device associated withsaid bridged circuit and selective of one of tlie car-rier frequenciesto be transmitted tlirougli tlie amplilier, carrier receiving equipmentassociated ivitli said selective circuit, a second-bridged circuitassociated ivilli tlie amplifier patli, said second circuit including aselective device selective of a frequency correspondingto the frequencyselected by said first mentioned selective device, carrier transmittingequipment for controlling tlie transmission of said frequency tlirouglisaid .second selective circuit, a. Morse sender foi controlling saidcarrier transmitting equipment and a Morse receiver controlled by saidAcarrier receiving equipment.

1G. In a signaling system in vfliicli the can rier frequenciescorresponding to a plurality of-cliannels transmitting in tlie sainedirection are amplilied by a common amplifier,

for obtaining intermediate subscribers loops comprising a bridgedcircuit associated vvitli tl'ie patli of said amplifier, a selectivedevice associated ivitli said bridged vcircuit and selective of one oftlie carrier frequencies to be transmitted tlirongli tlie amplifiencarrier receiving equipment associated with said selective circuit, asecond bridged circuit associated with `the `amplifier patb, said second,circuit including a selective device selective of a frequency cor.-responding to tlie frequency selected by said first mentioned selectivedevice, carrier transmitting equipment for ycontrolling the transmissionf said frequency tlirougli said second selective circuit, a Morse senderfor controlling said carrier transmitting `equipment, a llorse receivercontrolled lby Said arrier receiving equipment, and -a local loopinterconnecting said Morse receiver and Morse sender for relaying thesignals supeiposed on a .selected carrier frequency.

'i'. In a signalingsystem in which a common amplifier is .employed foramplifying all carrier frequencies transmitted from West te east and asimilar common amplifier is employed :for amplifying all carrierfrequencies transmitted from east 1to west, means for providingintermediate subscribers drops, said means comprising :a bridged circuitassociated with eacli of said anq-"ilitieis a selective ,deviceassociated with caen bridged circuit, one of said selective devicesbeing selective of a carrier frequency transmitted from -West to east,and tlieotlier selective device beingl selective'of the carrierfrequency transmitted fromeast to west, carrier receiving equipmentassociated -with ez cb of said selective devices, a second brit` gedcircuit being associated with the p atli .of eacli of said an'iplifiers,a` selective device associated avitli eacli of said second bridged.circuits and selective of frequencies corrcsponding` to tlie frequencyof tlie `selective device associated with tlie other bridged circuitoftlie same amplifier, carrier transinitting equipment for controlling thetransmission of the corresponding carrier frequency tlirougli eac-li ofsaid second vselect-ive devices, a Morse transmitter for controllingeacli carrier transmitting `equipment, and a Morse receiver associatedwith eacli carrier receiving equipment.

8. In a signaling system in which a com Imon amplifier is employed foramplifying all carrier frequencies transmitted from' vvest to eastand asimilar common amplifier is employed for amplifying all ycarrierfrequencies transmitted from east to West, means for .providingintermediate Subscribers drops, said means comprising `av bridgedcircuit associated with each of said amplifiers, a selective deviceassociated with each bridged circuit, one of said selective devicesbeing selective of a carrier frequency transmitted from West to east,and .the other selective device being select-ive of the carrierfrequency transmitted from east to West, carrier receiving equipmentassociated :with ueacli of said selective devices, a second bridgedcircuit being associated with bho lthe lective device associated withthe other bridged circuit of the saine amplifier, carrier transmittingequipment for controlling transmission of the (':oi'responding carrierfrequency through each of said second selective devices, a Morsetransmitter for controlling cach carrier transmitting equipment, a Morsereceiver associated with cach carrier receivingl equipment, and localsubscribers loops interconnecting` each Morse receiving equipment Withthe corresponding Morse sending equipment, so that the signals carriedby the selected carrier frequency transmitted from West to east Will berelayed through the local loop, and the signals carried by the selectedcarrier frequency transmitting from east to West will be relayed througha local loop.

9. In a. signaling system in which a common amplifier is provided in arepeater' path interconnecting t-Wo line sections for amplifying all ofthe carrier frequencies transmitted from one line section through therepeater path to the other line section in a given direct-ion, means forproviding intermediate subscribers drops, said means comprising a filterincluded in said repeater path for suppressing at least one of thecarrier frequencies transmitted in a given direction, a bridged circuitconnected to each side of said suppression filter, a selective deviceassociated With each bridged circuit and selective of the carrierfrequency suppressed by said suppression iilter, a carrier receivingequipment associated with one of said selective devices, carriertransmitting equip nient asi-:ociated with the other selective device, aMorse receiver controlled by said carrf er receiving eqn ipment and aMorse sender for controlling said carrier transmitting equipment.

l0. In a signaling' system in Which a common ampli lier is provided in arepeater path interconnecting two line sections for amplifying all ofthe carrier frequencies transmitted from one line section through therepeater path to the other line section in a given direction, means forproviding intermediate subscribers drops, said means comprising a filterincluded in said repeater path for suppressing at least one of thecarrier frequencies transmitted in a given direction, a bridged circuitconnected to each side of said suppression `tilter, a selective deviceassociated with each bridged circuit and selective of the carrierfrequency suppressed by said suppression lilter, a carrier receivingequipment associated with one of said selective devices, carriertransmitting equipment associated With the other selective device, aMorse receiver controlled by said carrier receiving equipment, a Morsesender for controlling said carrier transmitting equipment, and a localsubscribers loop for relaying signals from the Morse receiver to t-heMorse sender.

In testimony whereof, I have signed my name to this specification this22nd day of October, 1925.

BAXTER P. HAMILTON.

